Update appveyor to take into account now available packages.

appveyor.yml

@@ -1,26 +1,19 @@
-os: Visual Studio 2013
+os: Visual Studio 2015
 
 environment:
  CMAKE_ARGS: -DCMAKE_BUILD_TYPE=Release
- NSIS_ROOT: C:\nsis
- SSL_VER: 1_0_2k
 
 configuration:
  - Release
 
 install:
- - appveyor DownloadFile http:https://slproweb.com/download/Win32OpenSSL-%SSL_VER%.exe
- - Win32OpenSSL-%SSL_VER%.exe /silent /verysilent /sp- /suppressmsgboxes
- - appveyor DownloadFile ftp:https://sourceware.org/pub/pthreads-win32/pthreads-w32-2-9-1-release.zip
- - 7z -y x pthreads-w32-2-9-1-release.zip -oC:\pthreads\
- - cinst -y nsis
 
 build:
 
 build_script:
  - md build
  - cd build
- - cmake -DCMAKE_BUILD_TYPE=Release ..
+ - cmake -DCMAKE_BUILD_TYPE=Release -DWITH_THREADING=no ..
  - cmake --build . --config Release
  - cd ..
 
@@ -38,8 +31,3 @@ artifacts:
  #- path: build\client\Release\mosquitto_pub.exe
  #- path: build\client\Release\mosquitto_sub.exe
  #- path: build\src\Release\mosquitto.exe
-
-cache:
- - C:\OpenSSL-Win32
- - C:\pthreads
-